The present application is a competing renewal of a CCHI grant on the human immune response to Bacillus anthracis and the vaccine that protects the military, and that was first awarded in 2004. The goals of the original application were threefold: (a) To study the human immune response to a flawed vaccine, (b) To understand the mechanism for the high lethality of the inhalation form of the disease, (c) To understand the cellular basis of the host response to the pathogen. We have learned much about the human vaccine with our collection of nearly 3,000 samples, including samples of individuals who have naturally been infected with B. anthracis. Especially notable is our finding that fully 50% of vaccinees are unprotected. This is so, despite more than 6 vaccinations immunized against the pathogen's toxins in an onerous vaccine schedule. We have evidence, in contrast to prevailing views, that the high rate of mortality is due to bacterial sepsis and not the anthrax toxins. We made the seminal discovery that immune complexes of peptidoglycan and pre-existing serum opsonins present in all humans may be the source of the massive inflammation and coagulopathy accompanying infection by B. anthracis. We have new evidence that the infection is accompanied by release of proinflammatory and procoagulant nucleosome material (DAMPs) and that the anthrax toxins can modulate the clearance of this material. In this renewal application, we will follow up on these exciting discoveries to determine: (a) In the early- and mid-stage of disease, how are DAMPS released by the host, how they are cleared by the host innate immune system and how does toxin affect these processes. (b) In the late stage of the disease, how does opsonized peptidoglycan influence the outcome of the disease. (c) Why the vaccine is imperfect in stimulating the maturation of germinal center B cells in adults. These studies are supported by 2 scientific cores: An animal core that applies a non-human primate model we established in previous funding cycles and a flow cytometry core with state-of-the-art sorting and analyzing capacity. We also have a Technology Development Project that seeks to develop a generalized model by which pathogens, including anthrax spores but also other bacterial and viral pathogens, move across epithelial and endothelial barriers to infect tissue. The studies in this renewal application are focused and thematically organized around the key roles of peptidoglycan and the anthrax toxins in the human innate and adaptive immune responses. They have great potential to identify novel means of interrupting the pathology caused by this model Gram-positive pathogen.